I honestly have no idea why anyone thinks all of the Guardians will be showing up here. It makes a heck of a lot more sense to introduce a single new character in Avengers 2 than in does to take a half dozen characters from the Guardians movie and stuff them into Avengers 2.

This is a movie, not a comic. It's a major disservice both to this film and those characters to shove them all in this movie, instead of allowing the Avengers themselves time to continue to grow and develop as an ensemble.

I like the idea of Thanos being introduced before The Avengers 2, but I don't want the Guardians in the film, and I think you're right.